Ototoxic chemicals: why noise plus solvents lowers the limit

Short answer: because some chemicals can damage hearing on their own and add to the damage done by noise. Where employees are also exposed to ototoxic chemical agents, the Noise Exposure Regulations, 2024 apply the noise action level of 82 dBA, or a peak of 135 dBC, in place of the 85 dBA and 137 dBC noise-rating limit. Whole-body vibration above the action level in the Physical Agents Regulations, 2024 has the same effect.

The regulations were published as Government Notice 5953 in Government Gazette 52226 on 6 March 2025 and took effect on publication. They replaced the Noise-Induced Hearing Loss Regulations, 2003, which were repealed on 6 September 2026. The Department's launch presentation in April 2025 summed up the change: with concomitant exposure, the 82 dBA/135 dBC action level "becomes the noise rating limit where applicable".

What counts as an ototoxic chemical agent

The regulations define an ototoxic chemical agent as "a chemical agent with the potential to cause hearing impairment alone or in combination with noise, even below 85 dBA". They do not list any substances, and they set no chemical concentration below which the lower noise level stops applying. Instead, regulation 7(2)(f) requires the noise exposure risk assessment to take into account "the presence and extent of exposure to ototoxic chemical agents".

For practical guidance, see the 2018 bulletin on ototoxicity by the US Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health. Its examples of ototoxic substances, which are US guidance and not part of the South African regulations, include:

• Solvents: toluene, p-xylene, ethylbenzene, styrene, n-hexane, trichloroethylene and carbon disulphide.

• Metals and compounds: lead, mercury compounds and organic tin compounds.

• Asphyxiants: carbon monoxide, and hydrogen cyanide and its salts.

The bulletin notes that hearing loss "can be even greater with exposure to both ototoxic chemicals and noise than exposure to either noise or the ototoxic chemical alone". It names printing, painting, construction and manufacturing among the activities where the two exposures can combine.

What changes at 82 dBA

Where there is concomitant exposure, these duties start at 82 dBA, or 135 dBC, instead of 85 dBA or 137 dBC:

• Noise zones (regulation 11): work areas, and mobile plant, at or above 82 dBA must be designated and clearly demarcated.

• Monitoring (regulation 8): a noise exposure monitoring programme by an approved noise inspection authority.

• Hearing protection (regulation 12(2)(a)): HPDs must bring exposure below 82 dBA, so devices chosen for an 85 dBA target may not be enough.

• Medical screening and audiometry (regulation 9): affected employees must be included, with periodic audiometry every 12 months from 82 dBA to below 105 dBA under the Code of Practice for Audiometry.

Training must cover the risk too. Regulation 4(4)(c) requires employees likely to be exposed to noise to be trained, before exposure, on "ototoxic chemical agents and whole-body vibration acting synergistically with noise to cause hearing loss".

In practice, a spray booth, print room or degreasing area measured at 83 dBA must be treated as a noise zone if the people there are exposed to ototoxic solvents.

Two sets of regulations, one assessment

Regulation 2(3) states that where an employer exposes any person to an ototoxic chemical agent or to whole-body vibration, the Regulations for Hazardous Chemical Agents and the Physical Agents Regulations also apply. On the chemical side, that means an assessment of exposure under regulation 5 of the Regulations for Hazardous Chemical Agents, 2021 and, where that assessment shows employees may be exposed by inhalation, air monitoring by an approved inspection authority under regulation 6.

The two assessments need to inform each other. The noise survey shows which areas and tasks fall between 82 and 85 dBA. The chemical assessment shows who is exposed to which substances. Without both, you cannot tell which noise level applies to whom. Regulation 7(2)(g) adds the same check for whole-body vibration against the action level in the Physical Agents Regulations.

A quick self-check

• List the chemicals used in or near each noisy area: paints, thinners, glues, degreasers, fuels, and processes that produce lead fume or engine exhaust.

• Check each safety data sheet for effects on hearing, and ask the supplier where it is unclear.

• Mark every area and task between 82 and 85 dBA in your noise survey report, and compare that list with the chemical list.

• Confirm that your noise risk assessment records ototoxic chemical exposure and whole-body vibration, as regulation 7(2)(f) and (g) require.

• Check that hearing protection for those workers brings exposure below 82 dBA.

• Make sure affected employees are in the audiometry programme and have been trained on combined exposure.

How Qualitas can help

Qualitas Occupational Consulting is a Department of Employment and Labour Approved Inspection Authority and a SANAS-accredited (ISO/IEC 17020) inspection body for asbestos, lead, noise and hazardous chemical agents. Because both exposures fall within that scope, we can assess them together. Our noise surveys identify the areas and tasks between 82 and 85 dBA, and a hazardous chemical agents survey measures airborne exposure to the chemicals used there, in reports written for management, SHEQ teams and auditors.

For the next steps, see when a work area has to be a noise zone and what the Hazardous Chemical Agents Regulations, 2021 require.

Not sure what your site needs? Start with our free Compliance Gap Analysis, request a quote, or call or WhatsApp 082 649 6599.

This article is general guidance based on the Noise Exposure Regulations, 2024 (Government Notice 5953, Government Gazette 52226, 6 March 2025) and the Regulations for Hazardous Chemical Agents, 2021 (Government Notice R. 280, Government Gazette 44348, 29 March 2021). It is not legal advice; refer to the regulations for the full requirements.

Christo de Wet is a SAIOH-registered occupational hygienist with 15 years' experience and the founder of Qualitas Occupational Consulting.